The present invention relates as indicated to an anti-theft locking device, and more particularly to a locking device particularly adapted to be used in a system for preventing unauthorized removal of articles from department stores, boutiques, or the like. In accordance with the invention, the locking device is securely mounted in an identification tag, with the lock being securely attached to articles of merchandise in such a manner that the lock can be opened or separated only by the use of a special tool which can be conveniently located at the checkout point in the department store or similar establishment. The lock tightly frictionally engages a pin which extends through the protected article, with the actuation of the tool permitting the pin to be released and the lock and tag removed from the article for normal purchased items. If a person attempts to surreptitiously remove the article from the store without purchasing the same and consequently effecting removal of the identification tag and lock, the construction of the tag and the complete system permits an alarm system to be actuated at an exit point or points in the store thereby notifying the store operators of the unauthorized removal of the article from the premises.
Locking devices similar in purpose to the locking device of the present invention are disclosed in U.S. Pat. Nos. 3,858,280 to Martin A. J. Martens and 3,911,534 to Henry J. Martens et al. Reference is specificially made to these patents for a complete understanding of the anti-theft system and the specific construction of the identification tag with which the locking device of the present invention is employed. It should be noted in this regard that the identification tag has been disclosed in the present application drawing and will be referred to hereinbelow only for a full understanding of the present invention, with the construction of the tag forming no part thereof. Similarly, the detaching tool by means of which the locking device can be separated from the article secured thereto forms no part of the present invention, and reference is made to U.S. Pat. No. 3,911,534 which discloses a detaching tool which can be satisfactorily employed with the locking device of the present invention.
With regard to known prior art, the most relevant art which applicants are familiar with is the aforesaid U.S. Pat. No. 3,911,534, of which applicants are joint patentees. In the patented fastening device, positioned within the housing or cap of the fastener is an insert containing both a longitudinal opening for receiving the pin and transverse openings for receiving the retaining balls. The latter, upon insertion of the pin into the insert and housing, were cammed against an anular ring frictionally retained within the housing around the insert. Upon insertion of the pin, the insert was caused to move upwardly within the housing against spring bias, with release of the pin preventing the same from being withdrawn due to the tight frictional engagement of the ball surfaces with the pin and the adjacent surfaces of the ring. Removal of the pin was effected by placing the fastening device adjacent the detaching tool which, when actuated, electromagnetically moved the insert, formed of magnetizable material, upwardly in the housing thereby permitting the retaining balls to move upwardly along the cam surface of the ring and out of tight frictional engagement with the pin. The pin and tag with the fastening device could then be removed and separately stored for reuse.
Although the above described structure provided highly satisfactory results in commercial use over an extended period of time, it did possess certain disadvantages in terms of cost both with respect to material parts and also labor costs required to assemble the fastening device.